This invention is generally in the field of medical devices, and more particularly catheters for use in interventional cardiology.
Catheters are often used in the performance of medical procedures such as coronary angiography for injecting dye, or the like, into the cardiovascular system for diagnosis; and angioplasty to widen the lumen of a coronary artery which has become at least partially blocked by a stenotic lesion causing an abnormal narrowing of the artery due to injury or disease.
Interventional cardiology is a medical subspecialty in which a guiding catheter is used to insert balloons, stents, and other therapeutic devices (e.g., laser catheters, atherectomy catheters) into arteries supplying blood to the heart muscle, i.e., coronary arteries, to open fatty blockages, e.g., percutaneous transluminal coronary angioplasty. These devices move through an axial lumen in the catheter. Generally, a catheter is inserted into an artery in the groin or wrist of the patient and advanced into the aorta. The tip, or distal end, of the catheter then is inserted into the ostium (the opening) of a coronary artery, one of three small vessels branching off the aortic root (the base of the aorta) around the heart. The opposite, or proximal, end of the guiding catheter, through which balloons stents or other devices are introduced and advanced into the lumen of the guiding catheter, remains outside of the patient's body. The balloon or other device is advanced through the lumen of the catheter, out an aperture in the tip, and into the coronary artery to the blockage.
Varying degrees of resistance to balloon advancement are encountered, depending upon several factors, such as tortuosity, calcification (or stiffness), and size of the coronary artery. This resistance translates into an equal and opposite force onto the guiding catheter, which undesirably tends to back the guiding catheter out of the coronary ostium. The force or support with which a particular catheter can exert to oppose this retreat and maintain the position of the tip within the vessel ostium determines the catheter's ability to allow passage of balloons or other devices, for a successful interventional procedure.
There are varying catheter design approaches for dealing with this advancement resistance. For example, a catheter design may be based upon the curvature of the catheter tip, as well as on the thickness and stiffness of the wall of the catheter. “Aggressive” catheter designs, such as Amplaz or Voda type, provide for “deep seating” of the tip further into the vessel and afford greater maintenance of tip position “backup support” while advancing the balloon. The disadvantage of these catheters, however, is an increased risk of vessel trauma or dissection, as the tip is forcefully engaged in the vessel ostium. Conversely, “conservative” catheter designs, such as Judkins, are more flexible and insert only minimally, atraumatically, into the coronary ostium. The drawback of this design, however, is that it offers less backup support and consequently increases the potential failure to deliver the balloon or other device to the target blockage. In addition to backup support, the locations of the coronary arteries are extremely variable among patients, necessitating multiple curvature designs to accommodate the wide array of anatomical variations.
Therefore, the selection of catheter is a critical part of an interventional procedure. Oftentimes, multiple different catheters need to be tried before an appropriate one is identified. Such multiple catheter exchanges can jeopardize patient safety, frustrate the physician, increase the cost of the procedure, and increase the cost of providing the inventory of catheters. At times, the physician may have to accept a suboptimal result because a superior, but bulkier, device such as a stent is not deliverable without adequate guiding catheter backup support. It would be desirable to take some of the “guesswork” out of guiding catheter selection, both for considerations of backup support as well as anatomic variations. It would be desirable to provide a single, versatile catheter, combining favorably features of aggressive designs and conservative designs as needed.
U.S. Pat. No. 5,098,412 to Shiu discloses a support system for a guiding catheter. The catheter comprises a main lumen and a secondary lumen, which are connected integrally together throughout the proximal portion of the length of the catheter but are separated throughout a distal portion. An incompressible, flexible, elongate element is slidably disposed within the secondary lumen and is anchored at the distal end of the catheter. The proximal end of the catheter includes operating means to exert an endwise force on the elongate element to cause the separated portion of the secondary lumen to move away from the main lumen to brace the catheter against opposite walls of the aorta for “backup” support and to retain it in a selected position. This design, however, requires two full lumens, each having its own wall structure all the way around the lumen perimeter. This feature results in a double layer of sleeve material where the sleeves of the two lumens interface, adding thickness to the catheter device, causing it to have a larger profile without a corresponding increase in lumen diameter, even though it is highly desirable to maximize the ratio of the inside diameter of any functional lumen to the outside diameter of the tubular body in coronary arterial applications. That is, for a given lumen diameter sized to accommodate a particular balloon or other therapeutic device, the catheter desirably has as small a profile, or sheath size, as possible in order to minimize arterial trauma (e.g., trauma to the femoral artery). In another aspect, it would be desirable to provide means for more finely controlling the position of the backup support member, the position of the distal tip of the primary catheter, or both, in order to enhance the versatility of a single catheter design.